A combine harvester is a machine that is used to harvest grain crops. The objective is to complete several processes, which traditionally were distinct, in one pass of the machine over a particular part of the field. Among the grain crops that may be harvested with a combine are wheat, oats, rye, barley, corn, soybeans, flax or linseed, and others. The waste (e.g., material other than grain (MOG)) discharged on the field includes the remaining dried stems and leaves of the crop which may be, for example, chopped and spread on the field as residue or baled for feed and bedding for livestock.
A combine harvester cuts crop using a wide cutting header. The cut crop may be picked up and fed into the threshing and separating mechanism of the combine, typically consisting of a rotating threshing rotor or cylinder to which grooved steel bars commonly referred to as rasp bars or threshing elements may be bolted. These rasp bars thresh and aid in separating the grains from the MOG through the action of the drum against the concaves, i.e., shaped “half drum,” that may also be fitted with steel bars and a meshed grill, through which grain, chaff and smaller debris may fall, whereas the straw, being too big or long, is carried through to the outlet. The chaff, straw, and other undesired material (MOG) are returned to the field via a spreader mechanism.
In an axial flow combine, this threshing and separating system serves a primary separation function. The harvested crop is threshed and separated as it is conveyed between a longitudinally arranged rotor and the inner surface of an associated chamber comprising threshing and separating concaves, and a rotor cage or cover. The cut crop material spirals and is conveyed along a helical path along the inner surface of the chamber until substantially only larger residue remains. When the residue reaches the end of the threshing drum, it is expelled out of the rear of the combine. Meanwhile, the grain, chaff, and other small debris fall through the concaves and grates onto a cleaning device or shoe. For ease of reference, this smaller particulate crop material that contains the grain and chaff is referred to as threshed crop. The grain still needs to be further separated from the chaff by way of a winnowing process.
Clean grain is separated out of the threshed crop by way of a flat oscillating cleaning system that can include a chaffer and sieves. Generally, the cleaning system operates by mechanical and pneumatic methods; blowing air through the threshed crop to winnow the chaff and then sieving the grain to separate the grain from other particulates. Clean grain that is separated from residue via the sieves is typically transported to a grain tank in the combine for temporary storage. The grain tank is typically located in an upper portion of the combine and loaded via a conveyer that carries clean grain collected in the cleaning system to the grain tank.
The conventional grain tank is arranged such that grain conveyed from the cleaning system fills the tank while inclines in the tank floor allow the grain to be gravity-fed into a transversely-oriented cross auger. By virtue of gravity feed and cross auger, grain may be distributed to a single point in the grain tank, such that another conveying system can offload the grain from the grain tank. Offloading the grain is typically implemented in one of either two conveying systems. One type of offload system is a turret style system. The turret style system incorporates a vertical auger within a vertical tube. At the top of the vertical tube, an unload tube, which may include a horizontal auger, connects and pivots coextensive with the vertical tube. A long-top unload tube may be used during the harvest to unload grain to a support trailer or vehicle. The other offload system is a swivel system. The swivel system incorporates an unloading auger attached to the cross auger, angled upward from the vehicle and pivots at the side of the vehicle to offload grain. The grain in a swivel system may too collect in a support trailer or vehicle. Both systems allow large quantities of grain to be offloaded in the field without needing to stop harvesting when the grain tank fills.